Distillation of hydrocarbon oils for the production of lower boiling hydrocarbon oils



Apml 14, 1936. w H BAHLKE ET AL 2,037,674

DISTILLATION OF HYDROCARBON OILS FOR THE PRODUCTION OF LOWER BOILING HYDROCARBON OILS Filed Dec. 18, 1950 Patented Apr. 14, 1936 UNITED STATES DISTILLATION OF HYDROCARBON OILS FOR THE PRODUCTION OF LOWER BOILING HYDROCARBON OILS William H. Bahlke, Hammond, and Walter G.

Whitman, Whiting, Ind, assignors to Standard Oil Company, Whiting, Ind, a corporation of Endiana Application December 18, 1930, Serial'No. 503,320

7 Claims.

, with the accompanying drawing, in which,

Figure 1 is a side elevational view, diagrammatic in character, partly in section and partly broken away, of apparatus suitable for carrying.

out the present invention.

Figure 2 is an enlarged fragmentary vertical sectional view of the lower portion of the fractionating column showing suitable means for v injecting liquid thereinto; and

Figure 3 is an enlarged longitudinal vertical section of suitable means for introducing liquid :into the lower portion of the fractionating column.-

Figure 1 illustrates, diagrammatically, apparatus for carrying out a well known type of pressure distillation or cracking'process. processes the 011 to be cracked is passed through an elongated restricted passageway, such as a pipe coil, wherein it is heated to cracking or conversion temperature. The he'ated oil. is discharged intoan enlarged chamber wherein it is maintained at cracking temperature for a sub-- stantial period of time. The vaporous products are withdrawn from the chamber and are passed to a fractionating column, such as a bubble tower, wherein certain of the higher boiling prod- .ucts undesired in the final distillate product are condensed and thereby separated from the vapors. The condensed heavier constituents are withdrawn from the fractionating column and are introduced into the restricted heated passageway or pipe coil and thus are admixed with the fresh charging stock, and subjected to cracking conditions of temperature along with the fresh stock. The fractionatedvapors are condensed and subjected to the usual refining treatment.

We have observed that in the above type of processes, the heavier constituents condensed from the vaporous products and which are returned to the stream of fresh charging stock, normally, are responsible for certain inefiiciencies in the process. For example, these heavy condensates contain certain portions which do not readily crack under the temperature and pressure conditions best adapted for the fresh rstock and-consequently-tend to accumulate in In such the system and thus reduce the capacity of the same. Also these products are difficult to-pump back into the fresh oil stream in that theytend to vaporizeat the temperature at which they are maintained in the bottom of the fractionating tower, thus causing substantial vapor looking within the pump. employed for forcing them into the stream of fresh stock.

We have found that the above mentioned disadvantages can be substantially minimized by introducing a liquid, for example, an aqueous fluid such as water into the heavy condensates before they are withdrawn from the lower portion of the vapor fractionating column. The liquid is heated by the hot condensates and is converted into vapor which bubbles up through the body of hot condensate and strips from them a substantial portion of the heavier constituents which are not adapted to be cracked with'the fresh stock. These heavy portions are known in the art as naphtha bottoms. The liquid when introduced in amounts sufficient to form the quantity of vapor necessary to effect the desired stripping, functions to cool the condensates to a point at which they do not form suflicient vapors tocause'substantial vapor-locking of the pump which charges them into the cracking coil. The capacity of the cracking process is thus substantially increased since the fractions diilicult to'crack, in conjunction with the fresh stock, do not tend to accumulate in the system and are substantially removed from the heavy condensate or reflux before it is passed to the pipe coil and admixed with the fresh stock undergoing cracking.

It is to be understood that the present invention may be employed with any other type of cracking process wherein the heavier undesired constituents are condensed from the desired vaporous products and returned to the original cracking operation.

Referring more in detail to the drawing, the numeral 5 indicates a furnace setting in which is mounted a pipe coil 6 "through which the oil to be converted or cracked is passed. The oil to be treated may be drawn from any suitable source through a line I, by pump 8 from which it is discharged through a line 9, to a coil I0 disposed within the upper portion of a fractionating column I l whereby the oil partially cools the vapors in the upper portion of the column. The partially heated oil is discharged from the coil l0 into a line [2 through which it is passed to the coil 6 mounted in the furnace 5 The oil is brought to cracking temperature within the coil 6 and is passed therethrough under a suitable pressure and at a velocity suflicient to avoid substantial cracking and deposition of coke within the coil 6.

The highly heated oil is discharged from the coil 6 through a line I3 into the lower portion of an enlarged reaction chamber I4 wherein it undergoes further cracking. The oil in chamber I4 may be maintained under substantially the same pressure at which it was discharged from coil 6, although it is to be understood a suitable pressure reducing valve (not shown) may be provided in line I3 for the purpose of maintaining a lower pressure in the chamber I4. The non-vaporous products are withdrawn from the lower portion of the chamber I4 and passed from the system through a valved line I5. The vaporous products are withdrawn from the upper portion of chamber I4 through a line I6 and are passed to the lower portion of the fractionating column II.

The column II may contain any suitable fractionating means for example a spaced series of plates of the ring and disk type or of the bubblecap type shown diagrammatically at H in Fig. 2. The vapors pass upwardly through the fractionating elements in column II and come into' intimate contact with downflowing cooler liquid, whereby they are fractionated, the heavy constituents undesired in the final distillate product being condensed and thereby separated from the vapors. The fractionated vapors flow through a trap-out plate I8 and into the upper portion of the column II containing the coil ID through which is passed the fresh oil to be cracked; The vapors give up a portion of their heat to the oil in the coil I0 and the heavier constituents thereof are condensed. The remaining vapors pass out of the column II through a line I9 leading to suitable condensing means, (not shown) The portions of the vapors condensed by the cooling medium in coil I0 accumulate on the trapout plate I8 from which any desired portion of such condensate may be withdrawn by line 20 and passed to the line I9 leading to the aforementioned condensing means. The remaining condensate overflows the trap-out plate I8 and thus provides a reflux cooling medium within the portion of the column therebelow.

The heavy condensed constituents undesired in the final distillate product are withdrawn from the bottom of column II through a line 2| and are passed therethrough to a pump 22. The hot condensates are forced from the pump 22 through a line 23 from which they are discharged into the pipe coil 6 at an intermediate point thereof. The heavy condensates become admixed with the fresh stock within the coil 6, flow through the remainder of the coil 6, being heated therein to cracking temperature and are passed on through the system along with the highly heated fresh stock. It is to be understood that these recycled heavy condensates may be returned to any point in the coil 6, and may, if desired, be introduced into the line I2 leading to the inlet of coil 6.

As previously stated, these heavy condensates withdrawn from the lower portion of column II, contain certain portions which are difficult to crack under the conditions of operation most suitable for the fresh stock. These portions are ordinarily termed naphtha bottoms in the art, and since they are difiicult to crack, they tend to accumulate in the system and thus reduce the temperature at which its vapor pressure is sufficiently high that it forms vapor in the pump 22 in suflicient quantity to greatly reduce the chiciency of the pump.

In order to strip these undesired constituents from the hot condensate and at the same time cool the condensate to such a point that its vapor pressure will not be sufficiently high to form an undesired quantity of vapors in the pump 22, a quantity of liquid vaporizable at the temperature of the condensate, such as water, is admixed with the hot condensate in the bottom of the column II. The liquid is heated by the condensate and converted into steam, which bubbles up through the condensate and strips therefrom a substantial portion of the constituents contained therein which are diflicult to crack along with the fresh stock in coil 6, i. e. naphtha bottoms. The liquid when introduced in quantities sufficient to effect the desired stripping action functions to cool the hot condensate to a temperature at which no undesired quantity of vapors will be formed in the pump 22.

This cooling and strip-ping liquid may be introduced into the bottom of column II through a line 24 provided with an adjustable valve 25 and a back-check valve 26. A valved line 2'! leads from a suitable source 29 of water and communicates with the line 24. The line 21 is provided with a force pump 3I.

It is preferred to provide the line 24 with a nozzle-like member 33 which discharges into the fractionating tower II. This nozzle 33 preferably comprises a tubular portion 34 provided with a small outlet 35. The tubular member 34 is fitted into a cylindrical sleeve 36 carried by a wall of the fractionating tower II and provided with an outwardly flared end 31 adapted to engage an annular shoulder 38 formed upon the tubular portion 34 at a point spaced from the outer end thereof. The pipe 24 has secured to its end a cylindrical sleeve 39 adapted to surround the tubular member 34 and which is provided with an outwardly flared end 40 adapted to engage the other face of the annular shoulder 38. The sleeves 36 and 39 are maintained in contact with the shoulder 38 by means of a pair of annular rings M and 42 one of which engages the flared end 31 and the other of which engages the flared end 40. The rings 4| and 42 are forced toward each other by means of a plurality of bolts 43, whereby the entire assembly is secured together in a leak-proof manner.

.In the operation of the process, barrels of fresh stock to be cracked were passed through lines I, 9, coil I0, line I2 and coil 6 wherein it was heated under superatmospheric pressure together with the hot condensate recycled from the bottom of column I I, to about 8'70 to 875 F. The vaporous products withdrawn from the top of chamber I4 were passed to column II. The vapors withdrawn from the top of column II were at a temperature of about 550 F. and the hot condensates in the bottom of column I I were at a temperature of about 785 F., and were formed at the rate of about 1.55 times the amount of fresh feed i. e. about 200 to 202 barrels per hour. The condensate on trap-out plate I8 was at 666 F. When water at atmospheric temperature was introduced through the line 24 into the column II at the rate of two gallons per minute it was found that the amount of backtrap or hot condensate withdrawn from the bottom of column II amount of fresh feed i. e. to 137 barrels per was about 1.05 times the hourpand wassatqa ,temperature of 7705971 The vapors withdrawn from the top of column. II were at,543-. F; and the condensate ontrap-out .plate I8 was at 672? F.

strokespertminuteto 38v strokes-per minute. The

introduction of water .caused: the amount of. naphtha bottoms in the. reflux condensate in.

columni-l I to lee-substantially reduced.

In processes of Ithenabove described type, a substantial superatmospheric pressure is main- :tained throughout the system. For example, in

the above described specific operation,: the

column] I was maintained underv3l0ilbs. pres-'- sure. In order to insure unvarying conditions of operation, it is desirableto force the aqueous afiuid into column ll under a pressure considerably greater .than that employed in the column I I. Fern-example, when a-pressure of 310 lbs. is maintained upon the column I l, the water may be forced thereinto under a pressure of 600 lbs.

Although the present invention has been described in connection with thedetails of specific embodiments thereof, it is not intended that such details shall be regarded as limitations upon the scope of the invention, except in so far as included in the accompanying claims.

We claim:

1. In the conversion of hydrocarbon oils wherein such oil is heated to cracking temperature under substantial pressure, vaporous products being separated therefrom and subjected to fractional condensation, the uncondensed vapors being removed from the system and the condensate collected in a body at a temperature normally above 700 F. and while in heated condition being returned by applied mechanical force to the original body of oil undergoing cracking, the step of introducing an aqueous liquid directly into said body of condensate which would normally be at said temperature above 700 F. formed in the fractional condensation operation to strip and partially cool same and. reduce the quantity of vapors therefrom before said condensate is returned to the body of oil undergoing cracking to substantially prevent vapor-locking of said applied mechanical force, said aqueous liquid being of such a boiling range that it will be substantially entirely vaporized by the hot condensate.

2. The method of converting hydrocarbon oils into lower boiling hydrocarbon oils which comprises, heating said oil to a cracking temperature, separately withdrawing vaporous products and subjecting them to fractional condensation whereby the insufliciently cracked constituents thereof are condensed and collected as a body of liquid oil at a temperature normally above 700 F., withdrawing the fractionated vapors from the system, returning by applied mechanical force the condensate while in heated condition to the oil undergoing cracking, and introducing a relatively cooler aqueous liquid in a stream of restricted cross-section directly into said body of condensate which would normally be at said temperature above 700 F. to cool same and reduce the quantity of vapors therefrom before passing the condensate to the oil undergoing cracking to substantially prevent vapor locking of said applied mechanical force, the aqueous liquid introduced being substantially entirely converted into steam and lighter constituents are stripped from said condensate thereby.

'pletely vaporized directly into'said body of hot condensate which would normally be at said temi perature above 700 F. to reduce the quantity of I vapors before the latter-is subjected to said'mechanically applied force wherein vapor locking thereof is substantially prevented inreturning";

the condensate-to the-oi-l undergoi Cracking- 4. 'The method of I converting hydrocarbonoils into lower boiling hydrocarbon oils which comprises, passing said oil through a restricted elongated passageway wherein it is heated to cracking temperature, discharging the highly heated oil into an enlarged chamber wherein it is maintained at cracking temperature, withdrawing vaporous products from said chamber and passing them to a fractionating column wherein the insufficiently cracked constituents are condensed and collected in a pool in the lower portion of said colunm at a temperature normally above 700 F., withdrawing the fractionated vapors from said column, withdrawing the hot condensate from the lower portion of said column and returning the same by applied mechanical force to the oil flowing through said elongated passageway, and introducing a relatively cool lower boiling aqueous liquid to be substantially entirely vaporized directly into the pool of hot condensate which would normally be at said temperature above 700 F. before it is withdrawn from said column and passed to said passageway in the manner aforesaid to cool said condensate and reduce the quantity of vapors therefrom to substantially prevent vapor locking of said applied mechanical force.

5. The method of converting hydrocarbon oils into lower boiling hydrocarbon oils which comprises, passing said oil through a restricted elongated passageway wherein itis heated to cracking temperature, discharging the highly heated oil into an enlarged chamber wherein it is maintained at cracking temperature, withdrawing vaporous products from said chamber and passing them to a fractionating column wherein the insufiiciently cracked constituents are condensed and collected in a pool in the lower portion of said column at a temperature normally above 7003" F., withdrawing the fractionated vapors from said column, withdrawing the hot condensate from the lower portion of said column and returning the same by a pump to the oil flowing through said elongated passageway, and introducing a relatively cool lower boiling aqueous liquid to be substantially entirely vaporized directly into the pool of hot condensate which would normally be at said temperature above 700 F. before it is withdrawn from said column to reduce the quantities of vapors and passed to said passageway by said pump without vapor locking thereof.

6. The method of converting hydrocarbon oils into lower boiling hydrocarbon oils which comsufiicient cracked constituents thereof are condensed under superatmospheric pressure and collected in a pool at a temperature normally above 700 I F., withdrawing the fractionated vapors from the system, returning by applied mechanical force the condensate While in a heated condition to the oil undergoing cracking, and supplying water free from extraneous treating materials in a stream of restricted cross-section and at a substantially higher pressure than existing during fractional condensation directly into the pool of condensate which would normally be at saidtemperature above 700 F. formed in the fractional condensation operation in a proportion that is completely vaporized to partially cool and strip the condensate before it is returned to the body of oil undergoing cracking and reduce the quantity of vapors therefrom to substantially prevent vapor locking of said applied mechanical force.

7. In the conversion of hydrocarbon oils wherein such oil is heated to cracking temperature while being maintained under superatmospheric pressure, vaporous products being separated therefrom and subjected to fractional condensation, the uncondensed vapors being removed from the system and the condensate collected in a body and while in heated condition being returned by applied mechanical force to the original body of oil undergoing cracking, the step of passing an aqueous liquid directly into said body of condensate formed in the fractional condensation operation to strip and materially cool same and reduce the quantity of vapors therefrom before said condensate is returned to the body of oil undergoing cracking to substantially prevent vapor locking of said applied mechanical force.

WILLIAM H. BAHLKE. WALTER G. WHITMAN. 

